Telephone system



Oct. 2, 1945. H. P. MAHONEY TELEPHONE .SYSTEM Filed Jan. 8, 1944 5Sheets-Sheet 1 oom OM LLDOWEO OKOO UW: M J.

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INVENTOR. HARRY R MAHONEY AT'LORNEYS Oct. 2, 1945.

H. P. MAHONEY TELEPHONE SYSTEM 5 Sheets-Sheet 2 Filed Jan. 8, 1944INVENTOR HARRY P. MAHONEY BY I ATTORNEYS Oct. 2, 1945. H. P. MAFIONEYTELEPHONE SYSTEM Filed Jan. 8, 1944 5 Sheets-Sheet 3 -45 low M GE BY Zi, [H

ATT 'ORNEYS Oct. 2, 1945. H. P. MAHONEY TELEPHONE SYSTEM Filed Jan. 8,1944 5 Sheets-Sheet 4 ATTORNEYS Patented Oct. 2, 1945 UNITED STATE sPATENT OFFICE TELEPHONE SYSTEM Harry P. Mahoney, Oak Park, 111.,assignor to Antomatic Electric Laboratories, Inc., Chicago, 111., acorporation ot'Delaware Application January 8, 1944, Serial No. 517,538

11 Claims.

invention relates to telephone systems and any expensive or complicatedtemporary or auxiliary equipment.

The problem of converting a manual telephone system to an automaticsystem, while maintaining service in the entire system while it ispartly manual and partly automatic, is complicated by the fact that anautomatic system is commonly operated on a voltage much higher than thatemployed in a manual system and by the further fact that the polaritiesof the line conductors in an automatic system are reversed as comparedwith the usual manual system. These factors present substantialdiificulties, particularly when theconversion from one system to theother extends over a considerable period of time during which both themanual and the automatic portions of the system are in operation andboth types of lines are to be interconnected.

Heretofore, it has been the practice, where such a conversion becamenecessary, to install special and temporary auxiliary equipmentincluding a call indicator switchboard comprising indicators adapted tonotify the operators at that'posltion of the numbers being called byautomatic lines,

thereby enabling the operator to extend the call manually to the calledsubscriber's line. Where the call originates on a manual line, theextension'of the call to the automatic lines has involved the provisionof special operator positions at the'automatic ofllce for completing theconnections extended thereto hy'the manual operators.

The present invention provides a solution for the above-mentioneddifiiculties without the use of'substantial auxiliary or temporaryadditional equipment by furnishing a system according to which themanual telephone system is directly connected to the automatic-system astheautoinatic system is progressively installed and the two systems arecoordinated for conjoint'oper ation by changes which are confined almostentirely to the manual equipment so that when the automatic system hasbeen entirely completed and supplants the manual system, the automaticsystem requires only minor alterations to adapt it to the usual or,standard automatic operation,

and the automatic portions or the so that there is no impairment orinterruption oi. service and no necessity for changing telephone numbersin any part or the system.

The primary object of the present invention is to provide an improvedmethod of eflecting the gradual conversion from manual to automaticservice according to which a system comprising manual equipment andautomatic equipment is arranged for interconnection and the extension ofcalls 'in both directions between the manual systems by changes whichconsist, primarily, in reversing the polarity of the lines, of themanual system to agree with the polarity of the lines of the automaticequipment and, at the same time, making a minor change in the operatingvoltage of the automatic system to approximate or harmonize with theoperating voltage of the manual system. A further object is to provide amanual telephone system comprising cord circuits of either the three.conductor type or the two conductor type, or both of these types, whichis directly connected with an automatic telephone system and in whichthe polarity of the linesand the operating voltages of the diiferentparts of the composite system are altered so that, with 1 a minimum ofadditional equipment, telephone calls originating in any part or thesystem may bev extended to subscriber stations in the other parts of thesystem to provide satisfactory service without the attention of specialoperatorsr Other objects relate to various features of the improvedsystem whereby a gradual and economic transition may be made from manualservice to automatic service while providing a uniformly good serviceduring the period of transition.

The nature of the invention will be understood from the followingspecification taken with the accompanying drawings in which a. telephonesystem embodying the present invention is illustrated. In the severalfiguresof the drawings, taken together, thereis illustrated, somewhatdiagrammatically, a complete system which is partly of the manual typeand partly of the automatic, the manual portion of the system beingshown in Figs. land 4 and 'the automatic portion in Figs; 2, 3 and 5. Itis assumed that in this illustrated system the conversion from manual toautomatic service is in the process of transition and that the necessarychanges have been made to permit the manual and the automatic portionsof the system to be operated to permit calls to be extended in eitherdirection between said portions of the system during the period whenboth portions of the system are operating.

2 During this period calls may, of course, be completed locally in eachexchange or between different exchanges of the manualsystem and the planof transition contemplates a gradual con- General description Beforedescribing the operation of the system or the details of the method ofconversion employed, some of the principal features embodied assaisowhich the operator causes outgoing calls from the two-wire cord circuit40 to be extended over the line In to a called subscriber line, such asthe line L400.

The three-wire cord circuit 30 comprises the answering plug I02, thecall plug I" and assoelated apparatus and circuit connections includindiflerent parts of the telephone system will be referred to.

, The manual portion of the telephone system comprises two divisions,shown in Figs. 1 and 4.

that portion of the system illustrated in Fig. 1 including three-wirecord circuits, such as the cord circuit 80, and that part of the systemillustrated in Fig. 4 comprising two-wire cord circuits, such as thecord circuit ll. This manual system includes a plurality of subscriberssub-stations, such as the stations M and MA, which are connected by thesubscriber lines LI and L4", respectively, with the contacts A of themain distributing frame MDF. These contacts A are adapted to beconnected by jumpers with the associated contacts B of the maindistributing frame and, in the portion of the circuit shown in Fig. 1,the contacts 3 are connected by the line lIla with the contacts D of theintermediate distributing frame IDF-I. Similarly, the contacts 3.

shown in Fig. 4 are connected by the line Illa with contacts D of theintermediate distributing frame lDF-I. Each subscribers line, such asthe line LI00, has associated therewith an individual manual linecircuit, such as the line circuit I05, and each subscriber's line of theother division of the manual system, such as the line L400, hasassociated therewith an individual manual line circuit, such as the linecircuit 405. Each line circult I05 includes a cutoff relay RI III and aline relay RI I5. Similarly, each line circuit 405 includes a cutoffrelay RIM and a line relay R4".

The contacts D of the intermediate distributing.

frame IDF-I, which are shown in Fig. 1, are

adapted to be connected by Jumpers with the contacts E which areconnected by lines, such as the line I00b, with jacks, such as the JackIOI, adapted to form a connection with the plug I02 terminating thethree-wire cord circuit 30. Similarly, the contacts D of theintermediate distributing frame IDF-I, which are shown in Fig. 4, areadapted to be connected by jumpers with other contacts E connected bylines, such as line 4002;, withjacks, such as the Jack "I, adapted toform a connection with a plug 402 terminating the two-wire cord circuit40. The terminals D of the intermediate distributing frame IDF-I,

shown in Fig. 1, are also connected by the line.

I00a with jacks, such as the jack I58, adapted to be connected with theplug I by which the operator causes outgoing calls from the threewirecor'd circuit 00 to be extended over the line Hills to a calledsubscriber's line, such as the line- LI00. In asimilar manner, thecontacts D of the intermediate distributing frame IDF-I, which are shownin Fig. 4, are connected by the line 460a with the multiple jacks, suchas lack 450, adapted to be engaged by the plug 455 by, 75 system wereconnected together without any rev ing the sleeve relays RI20 and RI,the supervisory relays RI20 and RI30, the ring relay RISII, a controlrelay RI, a ring cutoii relay RI", ringing generator I", the operator'sheadset IN and the talk key I00. A call originating in the manual systemshown in Fig. 1 may be extended through the multiple Jack I50 and overthe line 400! to subscriber stations of the division of the manualsystem shown in Fig. 4.

The two-wire cord circuit 40, shown in Fig. 4, comprises the answeringplug I02 and the call plug I. together with associated apparatus andcircuit connections including the sleeve relays R420 and R440, thesupervisory relays R425 and R4", the operator's headset I and the talkkey I. The portion of the manual circuit shown in Fig. 4 also includesthe multiple Jack 458 by which a connection may be made with a plug 405and through the line I000, a cordless B board 0, and a line I00! tosubscribers lines, such as the line LI00, terminating at the switchboardshown in Fig. 1.

As the manual system shown in Figs. 1 and 4 is organized, prior to anychanges which are made in the connections for the purpose of conversion,the circuits are connected to battery by the lead I" and to ground bythe lead I It by connections which are illustrated by dotted lines inFigs. .1 and 4. When the system operates with the dotted lineconnections, it customarily operates on a comparatively low voltage,such as a voltage of 24, which is common commercial practice. when themanual system is to be altered for operation in connection with a systemof the automatic type, the connections to battery and ground arereversed, as indicated above. but the same operating voltage is retainedin this manual portion of the system. As shown in Figs, 1 and 4, theconnections have been reversed. as indicated by full system. with thesleeve of a busy called line connected to battery by way of thecorresponding sleeve relay RI20 in the associated cord circuit and thetip of the calling. cord circuit connected to ground by way ofits'associated supervisory relay R I 30, the test for a busy conditionof such a line is made by momentarily connecting the tip of theassociated calling plug with the sleeve I of the multiple call jack ofthe busy called line, the busy v condition being indicated by a busyclick which is produced in the operator's headset as a result ofopposite potentials on the sleeve and the connected tip. In theoperation of an automatic system, on the other hand, the busy conditionof a line is indicated by the presence of ground on the conductorcorresponding to the sleeve conductor so that, if a manual and anautomatic versal of polarity, the usual busy test procedure would bring"together two parts having ground connections or two parts having.battery connections, so that a false busy test would be made and no trueindication of the busy condition given.

The automatic portion of the system shown in Figs. 2, 3 and 5 comprisesa number of automatic subscriber stations, such as the station P, towhich connections are made through automatic apparatus and linesincluding the link 200 comprising a finder Ill and a selector 220,together with a distributor 210, a connector 300, a trunk circuit 580, aselector 535, and a plurality of line circuits, such as the line circuit306, and .a plurality of lines, such as the line 300i, connecting theline circuits with the finder banks by way of an intermediatedistributing frame IDF2 through which connections are made with thefinder 2I0. The automatic system also includes a plurality of lines,such as the connecting line I00d, for connecting the automatic systemthrough the intermediate distributing frame IDF2 with the connectingline I00e which extends to the main distributing frame MDF of the manualsystem shown in Fig. 1. There is also included in the automatic system aplurality of lines, such as the connecting line 400d, extending from theconnector bank of the connector 300 to contacts G of the intermediatedistributor frame IDF-2 through which a connection is made with theconnecting line 400e extending to the main distributing irame MDF of themanual exchange shown in Fig. 4.

All of the parts of the automatic system referred to above are installedas a part of the origautomatic system, referred to above, it is alsonecessary during the period of conversion-to alter the voltages of thebusy relays of the connectors 800 and the cutoff relays of the linecircuits such as the line circuits 20I, WI and 305 to cause them toagree with the voltages of the manual system.

- During the period of conversion, the battery consystem isautomathz,these battery connections are shifted, as shown at H0 in Figs. 3 and 5,to connect the terminals of these busy and cutoff relays to a highvoltage battery, such as one having a voltage of 48, this being thestandard voltage on which other parts of the automatic system operatethroughout the period of conversion, as well as when the system has beenentirely converted.

In the drawings, the low voltage battery con- I nections have beendesignated LV and the high inal automatic equipment and function as suchthroughout the time that the automatic system is being used inconnection with the manual system for transmitting calls in bothdirections. In addition to these parts of the automatic system, otherautomatic apparatus and other lines are originally installed as a partof the automatic system but begin to function only as portions thereofare brought into use as the manual system is progressively convertedinto an automatic system. This additional equipment, which graduallycomes into use as a part of the automatic system during the process ofconversion, includes a plurality of line circuits, such as the linecircuit "I,

and a plurality of line circuits 50 I.

When the automatic system is originally installed, for intended use inconjunction with the manual system, it also includes a plurality oftemporary connecting lines 300a which extend from the jacks I59 of themanual system to terminals F of the intermediate distributing frameIDF-2 in the automatic system. Calls are extended over these lines 300afrom the manual system to the automatic system during the period ofconversion and when the conversion has been completed these lines 300amay be removed Also, during the period of conversion, the systemcomprises the jacks 459, adapted to be connected with the plugs 455 ofthe manual system, these jacks being connected by the lines 53I with thetrunk circuit 530 from which lines 532 extend to the selector 535. Whenthe conversion from manual to automatic service has been completed forthe manual system shown in Fig. 4, the jacks 459, lines MI and 532, andtrunk circuit 530 may be discontinued or removed.

In addition to the reversal of the polarities in the manual system whichis eflected for purposes of conversion to agree with the polarities ofthe voltage battery connections have been designated HV. The tip, ringand sleeve conductors of the manual system have been marked T, R and S,respectively. The conductors of the automatic lines which correspond tothe tip and ring conductors of the manual system have also been marked Tand R, respectively, and the third or control'conductor has been markedC.

In order that the operation of the invention may be more fullyunderstood, the manner of completing various telephqne connections,including the extension of calls from one manual station to another andof calls involving the use of both the manual and the automatic portionsof the system, will now be described. All of these operations aredescribed on the assumption that the above-described changes have beenmade for permitting the conjoint use of the manual and Assuming that themanual and the automatic systems have been interconnected as describedand that the battery polarity alterations have been made in the manualsystem as indicated in full lines, a subscriber at the manual substationM, desiring to call the substation MA, lifts his telephone, which causesa loop, including the line conductors of the line LI00, to be completedat the substation M. The completion of the loop at the substation Mcauses the line relay RI I5' to operate over a circuit from ground atcontacts III by way of the tip conductor of the lines I00c, I00a, and LI00, through the loop at substation M, over the ring conductorsof thelines LI00, I00a, and I000, the contacts I I2 and through the winding ofthe line relay RI I5 to battery. The line relay RI I5 operates over thiscircuit to complete, at contacts IIB, an obvious circuit for operatingthe answer lamp signal I03. To answer the call, the operator inserts theanswering plug of one of the cards. such as the plug I02 of the 'cordcircuit 30, into the jack IOI which is associated with the signal I03.When the sleeve of the plug I02 contacts the sleeve of the jack IOI, acircuit is completed for energizing in series the sleeve relay RI20 andthe cutoff relay RI I0. This circuit can be traced from ground at thelead II8, through the winding of the sleeve relay RI20, the sleeves ofthe plug I02 and jack IOI, and the winding of the cutoff relay RI I0 toLV battery on the con- V ductor II1. Inoperatins. the cutoi! relay RIIIinterrupts, at contacts III and 2, the circuit for energizing the linerelay RIII which then restores to open, at the contacts IIO, the circuitfor illuminating the answer lamp signal I 00. The sleeve relay I20, inoperating, completes, at the contacts I22 and I20, an obvious circuitfor connecting the operator's headset across the tip and ring conductorsof the cord circuit, this circuit including the normally closed contactsI50 and I54. The supervisory relay RI25 is also operated over the lineloop when the plug I02 is inserted into the jack IOI. This circuit maybe traced from ground at the lead I I0, by way oi the upper winding ofthe supervisory relay RI25, the ring conductor and ring contacts of theplug I02 and Jack IOI, over the loop at the substation M by way 01' theline LI00, the tip conductors of the Jack IN and plug I02, and the lowerwinding of the supervisory relay RI25 to battery upon the lead II1. Inoperating, the supervisory relay RI25 opens, at the contacts I25, acircuit for energizing a supervisory lamp I04. With the operator'sheadset II connected across the tip and ring conductor of the cordcircuit, which conductors are extended to the substation M through theassociated capacitors I41 and I40 and the plug I02 and jack IN, theoperator is in communication connection with the calling line LI00 andobtains the number of the desired line to be called. Also, when the plugI02 is inserted. into the jack IOI, the multiple jack I55 which isassociated with the line LI00 is marked as bus by the ground potentialwhich is applied to the sleeve conductor through the sleeve relay RI andover the line I00a. Ground upon the sleeve of the line I00a thereforemarks all of the multiple jacks associated with the line LI00 as busy,In addition,

ground potential is also applied to the sleeve conductor of theconnecting lines I00e and I00d from the sleeve of the jack IOI, whichground upon the sleeve conductor 310 marks the connecting line I00dassociated with the line LI00 as busy in the The sleeve relay Rllloperates in series with the cutoi! relay mm and opens, at contacts mconnector banks 0! the connectors, including the connector 300.

To extend the call to the substation MA, the plug I is inserted into themultiple jack I50, which is connected by the lines 400! and LI00 to thsubstation MA. In inserting the plug I55 into the jack I58, groundpotential is applied through the winding of the sleeve relay RI 50 tothe sleeve of the jack I58 and to the sleeve conductor of the line 400}.Ground upon the sleeve conductor of the line 4001 marks the line L400 asbusy in all the multiple jacks associated with this line in-both thesw'itchboards, and the multiple jack 455 has its sleeve grounded also byconnection with the sleeve conductor of the line 400! through the line400a. In addition to marking the line L400 "as busy at the manualswitchboards, the line L400 is also marked as busy in the banks of theconnectors, such as the connector 300, over the sleeve conductors of theassociated connecting lines 400e and 400d. The connecting line 4008 isconnected in multiple with the line 400! at the A contacts of the maindistributing frame MDF and is crossconnected to the connecting line 400dthrough the F and G terminals of the intermediate distributing frameIDF-2. The cutoff relay RAM is operated from the ground potential uponthe sleeve conductor of the line 400a to battery upon the lead I I1,and, in operating, this cutoif relay disconnects, at the contacts 4I2,the line relay R4I5 from the line conductors of the line 400k and I54,-the connections to the'operators headset IOI. The relay RI50, uponoperating, also completes, at the contacts I52, a circuit .102illuminating the supervisory lamp I51 which indicates to the operatorthat the call has not yet been answered. The automatic ringing oi thesubstation MA is initiated by the operation oi'the ring relay RIII, thisrelay being operated over a circuit including the contacts III and I42when the relay RI50 operates. In operating, the ring relay RI"completes, at the contacts I00 and III, a path for projecting ringingcurrent over the lines 400! and L400 In the substation MA.- This circuitmay be traced from battery upon the lead II1, through the ringinsgenerator I15 and the ring cutofl' relay RI45 in series, throughcontacts I05 to the tip of the plug I55; and from ground upon the leadIII through the resistor I15 and contacts I05 to the ring oi the plugI55. The tip and ring of the plug I55 are connected by way of the tipand ring of the lack I50 and the tip and ring conductors, respectively,oi the lines 400! and L400 to the ringer at the substation MA. Theringers respond to this ringing current, thereby notifying thesubscriber at substation MA that a call is to be answered.

To answer the call at the substation MA, the telephone is lifted fromits hook to complete a loop circuit over the tip and ring conductors ofthe lines L400 and 400i. These tip and ring conductors of the line 400!terminate upon the tip and ring of the jack I50 which has been connectedto the tip and ring of the plug I55, and the ring cutofl' relay RI45,being connected in series relation with the'loop and with the groundconnected resistor I16 and being connected to battery through thegenerator I15, is then operated over this loop.

The ring cutofl relay RI 45, in responding to the completion of the loopcircuit at the substation MA, operates to complete, at the contacts I45,an obvious circuit for energizing the relay RI40. The relay RI40operates and completes, at the contacts I, a locking circuit for itself,this circuit including the grounded contacts I5I which have been closedby the previous operation of the relay RI50. At the contacts I42, therelay RI40, upon operating, interrupts the circuit for. energizing thering relay RI35. The ring relay RI35 then restores to open, at thecontacts I38 and I30, the circuit for projecting ringing current overthe lines 400! and L400 extending to the substation MA. Also, the ringrelay RI35, in restoring, completes, at the contacts I01 and I39,connections between the tip and ring conductors of the calling end ofthe cord circuit with the tip and ring conductors oi the called end ofthe cord. Further, when the call at substation MA is answered tocomplete'the loop circuit at that station, the supervisory relay RI30 isoperated, over substantially the same loop circuit as that describedabove, and interrupts, at contacts I3I, the circuit for illuminating thesupervisory lamp I51. The operator at the switchboard is thereby advisedthat the called party at the substation MA has answered the call.

with the switchboard apparatus in this condition, the call fromsubstation M is extended by way of lines LI00, I00a, b, answering jackIN, the cord circuit 30, the multiple jack I50, and the lines 400! andL400 to the called station aaepnao V 5 MA. It is noted that the sleeverelays RI20 and RI50, the supervisory relays RI! and RI30 and the relayRI40 remain operated while the connection remains established betweenthe calling and called substations and untilthe connection is released.When the called party at the sub station MA hangs up, the loop circuitextending over the lines L400 and 400 is interrupted, thereby causingthe supervisory relay RI30 to restore. Upon restoration of thesupervisory relay RI30, the circuit for illuminating the supervisorylamp I51 is completed at the contacts I3I. The operator is thus advisedthat the called party has disconnected and the operator may withdraw theplug I55 from the jack I58. When the calling party at substation Mdisconnects, the circuit extending over the lines LI00, [a and 1001) isinterrupted to cause restoration of the supervisory relay RI25 whichcompletes, at the contacts I26, a circuit for illuminating thesupervisory lamp I04. The operator is thereby advised that the callingparty at the substation M- has disconnected and the plug I02 may bewithsleeve relay RI50, over the above-traced circuit to disconnect, atits contacts 33I and 332, the

line relay R395 from the subscriber's line L300.

The sleeve relay RI50, in operating, completes,

5 at its contacts I5I, a circuit including the condrawn from the jackIOI. When the plugs I02 and I55 are Withdrawn from their respectivejacks, the ground potential applied to thesleeve conductors throughtheir respective sleeve relays is removed, thereby causing the busymarkings to the associated jacks in the manual switchboards to beremoved and also the busy 'markings to the associated contacts in theconnector banks in the automatic system. Upon removal of the plug I55and the restoration of the sleevefirelay RI50, the contacts I5I areopened to interrupt the circuit for the relay RI40. Also, when the plugI02 is removed from the jack IOI, the circuit for energizing the cutoifrelay RI I0 in series with the sleeve relay RI20 is interrupted to causethese relays to restore. Likewise, when the plug I55 is removed from thejack I58, the relays R4I0 and RI50 are restored to normal. The equipmentof the manual system has now been restored to normal andmay be used toextend other calls.

Call extended from manual substation M to automatic substation P Inexplaining the connection from the manual substation M to the automaticsubstation P, it is assumed that the cord circuit has been used toanswer an incoming call from the substation M over the lines LI00, I00aand M01), and that the plug I02 has been inserted into the jack IOI. Itis also assumed that the supervisory relay RI25, the sleeve relay RI20,and the cutoff relay RI I 0 have been operated, as heretofore described.To extend this call to the substation P, the plug I55 is inserted intothejack I which terminates the line 300a extending to the F terminals ofthe intermediate distributing frame IDF-Z. When the plug I is insertedin the jack I59, the sleeve elements thereof are grounded through thesleeve relay RI50, and this ground extends over the sleeve conductor ofthe line 300a to a G terminal of the intermediate distributing frameIDF2 where the circuit divides, one branch xtending to the controlconductor 302 in the connector switch bank, and the other branchextending through the contacts 391 of the line relay R395 to the windingof the cutoff relay R390, and then to battery LV. Ground potential thusplaced upon the control contact of; the connector bank by the conductor382 marks the line 30012 as busy to the connector 300. The cutoff relayR390 then operates, in series with the tacts I42 for operating the ringrelay RI35 and thereby closes the contacts I36 and-I33 to cause ringingcurrent to be projected over the line 300a. This circuit for projectingringing current over the line 300a may be traced from battery upon thelead I I1 by way of the ringing generator I15, the winding of the ringcutoff relay RI45, the contacts I36 connected to the tip elements oi theplug I55, and the jack I59 and from ground upon the lead II8 by way ofthe resistor I16, the contacts I38 connected to the ring elements or theplug I55, and jack I59. The ringing current is thus conducted over thetip and ring conductors of the line 300a to the G terminals of the,IDF2,which terminals are cross-connected to the F terminals of the IDF--2.Since the line L300 extends from the F terminals of the IDF2 to theautomatic substation P, the ringing current is thus transmitted to thesubstation P. The subscriber at the automatic substation P, in answeringthe call, lifts the telephone from the switchhook to complete aloopcircuit which includes .the tip and ring conductors of the linesL300,

300a, the tip and ring elements or the Jack I53 and the plug I 55, thecontacts I36, the ring outoff relay RI45, the generator I15, andbattery, and the contacts I38 and the resistor I13 to ground. 1 e;

Asa result of completing the loop circuit at the substation P, the ringcutoff relay RI45 is operated to complete, at its contacts I45, anobvious circuit for the relay RI40. The relay Rl40'operates andcompletes, at its contacts I, a holding circuit for itself, this circuitincluding the ground connected contacts I5I which have been closed bythe operation of the relay RI 50. Also, in operating, the relay Rinterrupts, at its contacts I42, the circuit for energizing the ringrelay RI35, thus causing this relay to restore and interrupt, at itscontacts I 36 and I38, the circuit for projecting ringing current to thesubstation P. When the relay RI35 restores, a circuit is completed, atthe contacts I31 and I39, between the answering plug I02 and the callplug I55. The connection is now complete between the calling manualsubscriber substation M and the automatic subscriber substation Pthrough the associated lines embodied in the connection, and-theselinesare appropriately marked as busy by ground potential which has beenapplied to the sleeve conductors of each of the lines associated withthe calling and called substations.

The release of the calling line is effected as described hereinbefore.The release of the called substation P is initiated when the subscriberat that station hangs up to interrupt the loop circuit which extendsover the lines L300 and 300a to the cord circuit 30 and, moreparticularly, to the windings of the supervisory relay RI30. Thesupervisory relay RI30 is restored when the loop circuit is interruptedand completes, at the contacts I3I, a circuit including the contactsI52, to

illuminate the supervisory lamp I51; Upon ob-.

serving the lighted condition of the supervisory lamp I51, the operatorwithdraws the plug I55 from the jack I59 to remove the ground potentialfrom the sleeve conductors of the lines 300a and 300d. Removal of groundfrom the sleeve conductors of these lines removes the busy marking tothe equipment having access to these lines.

I Also, upon removal of-the plug I00. the sleeve Call from manualsubstation MA to manual substation M e In making a connection from themanual sub station MA to the manual substation M by way of the manualswitchboard shown in Fig. 4, the

subscriber at the substation MA lifts his telephone to complete a loopcircuit which includes the line relay R4I5. This circuit may be tracedfrom ground, at the contacts H I, by way of the tip conductors oi thelines 400e, 400a and L400, through the closed loop at the substation MA,the ring conductor of the lines L400, 400a and 400e, the contacts H2 01the cutoil' relay R4I0, and the winding of the line relay R4I0 tobattery. The line relay R4I operates and closes, at its contacts '4 I 0,an obvious circuit for illuminating the answer lamp 400 which lampnotifies the operator that relay R400 and through contacts 440 and 410to the tip oi the plug 400, the placing of the tip in contactwith a jacksleeve which is marked as busy with ground potential produces a busyclick in the receiver of the operator's headphone, due to the potentialdii'ierencebetween the grounded jack sleeve and the plug tip. Idle lineshave negative battery potential on the lack sleeve, and

when tested by applying the plug tip thereto no difference in potentialis encountered so no click is produced, which indicates that theassociated line is idle.

When the operator moves .the switch 400 to a closed position, theheadset 40I is connected across the tip andgring conductors of the cordcircuit 40 and a communication connection is thereby completed betweenthe calling substation MA and the operator's headset I, which connectionincludes the lines L400, 400a, 400b,

a call is to be answered upon the line L400. To V answer this call, 'aplug such as the plug 402 is inserted into the lack 40I, It is notedthat the plugs of the cord circuit 40-are of the type which have but twoelements, including a tip element which is arranged to make contact withthe tip spring of the iack 40l and a combination ring and sleeve elementwhich makes contact with both the ring. spring and the sleeve of thejack 40I. When the plug 402 is inserted into the Jack 40I, the cutoi!relay R4I0 is. operated'in series I with the sleeve relay R420 of thecord circuit 40 over a circuit which may be traced from ground upon thelead IIO, through the winding oi the sleeve relay R420, the ring-sleeveelement of the plug 402 the sleeve of the jack 40I, and through thewinding of the cutoi! relay R'4I0 to battery upon the lead I". Uponoperating, the cutoii relay R4I0 opens, at its contacts 4 and H2, the

circuit or the line relay R4I0. The supervisory relay R420 also operatesin series with the sleeve relay R420 over a circuit from ground upon thelead I I 0, throughthe sleeve relay R420, the ringsleeve element of theplug 402, the ring spring of the jack 40I, the ring conductors of thelines 400?), 400a and L400, through the loop at substation MA, the tipconductors oi. the lines L400, 400a and 40011, the tips of the jack '40Iand the plug 402, and

' through the supervisory relay R420 to battery on the lead, I IT. Thesupervisory relay R420, in operating, opens, at its contacts 420, thecircuit to the supervisory lamp 404. Ground potential, as supplied tothe sleeve conductor through the sleeve relay R420, is effective tomarkthe multiple jacks 400 of the line 400a as busy. Also, the jack I00is marked as busy by the ground potential which is applied to its sleeveby way ot the sleeve conductors of the lines 400b, 4004: and 400i. Thecon-'- trol contact in the connector bank or the connector 000, which isassociated with the lines L400, 400a and 400d, .is also marked as busyby the ground potential which is applied from the sleeve "relay R420through the sleeve conductors of these lines.

The usual busy test upon linesin manual telephone systems is made bybringing the tip of a cord circuit into contact with the sleeve of thejack which is associated with the line to be tested. With batterypotential on the tip 01' the. cord circuit, as, for example, in the cordcircuit 40, shown in Fig. 4, which has battery potential applied throughthe winding of the supervisory the jack 40I, the plug 402,the'capacitors 44'! and 440, and talking conductors of the cord 40 andthe switch 460. The operator may then obtain the number of the desiredline to be called and extend the call by inserting the call plug 400into theiack 400, which lack terminates the line I00a extending to thecordless B board 440. The operator at the cordlessB board 440 thenextends the call over the lines I00! and LI00 to the substation M in theusual manner.

Upon inserting the plug 400 into the lack 400. the sleeve relay R440 isoperated in series with a relay in the cordless B board 440 which issimilar to the usual .cutoil' relay in a line circuit.

4006. More particularly, the supervisory relay R400 operates by acircuit which extends from ground at the lead IIO to the sleeve relayR440 and then through the contacts 440 and4l4, the ring-sleeve elementof the plug 400, the ring spring of the jack 400, a loop in the cordlessB board, the tip conductor of the cord circuit, the tips or the jack 400and the plug 400, the contacts 410 and 440, and the supervisory relayR400 to battery on the lead III. In operating, the supervisory relayR400 opens, at its contacts 400, the circuit for lighting thesupervisory lamp 401, causing this lamp to'be extinguished and therebygiving an indication to the operator attending the cord circuit 40 thatthe operator at the cordless B board has answered the call. Alterascertaining the number 'of the called line from the manual operator,the operator at the cordless B board 440 tests the busy condition of thecalled line and it it is found to be idle completes the connection in awell known manner. In completing the call to the substation M over theline mu, ground potential is applied to the sleeve conductor of thisline by the equipment at the cordless B board 440. The sleeve conductorof the line I00! is connected, at the A terminals of the maindistributing frame MDF, to the sleeve conductors of the lines I00a andI00e. The sleeve conductors of the lines I00a and I00a are effective toextend the busy ground marking to the jacks I M and I 00, and also tothe control Contact in the connector banks of the connector 900 by wayof the line'l00d associated with called line L100.

Theanswering of the call at the substation M causes apparatus in thecordless B board 440 to respond, whereby the operator at this board isnotified that the call has been answered. When the plug 455 was insertedin the jack 459, the sleeve of the jack 458 was grounded from the groundwhich was applied through the winding of the sleeve relay R440 and thecontacts 449 and 414 to the ring-sleeve element of the plug 455. Thegrounding of the sleeve of the jack 459 marks the line 1009 as busy toany operators who may test this line at any multiple connected jacks atthe switchboard.

When the subscriber at the manual substation MA hangs up the receiver,the loop circuit extending over the line L400 is opened and this causesthe supervisory relay R425 to restore and close, at its contacts 426, acircuit, including'the contacts 42L for illuminating the supervisorylamp 404. The operator, upon observing the lighted condition of thesupervisory lamp 404,

the

is advised that the calling party at substation- MA has hung up and thatthe plug 402 may be withdrawn from the jack.40l. In withdrawing the plug402, the circuit for energizing in series the sleeve relay R420 and thecutoff relay R4l0 is interrupted, causing these two relays to restore.In restoring, the sleeve relay R420 opens, at its contacts 42l, thecircuit for illuminating the supervisory lamp 404. The cutoff relayR4l0, in restoring, prepares, at its contacts 4 and 412, the circuit forenergizing the line relay R415, Also, when the plug 402 is'removed fromthe jack 401, ground potential is removed from the sleeve conductors ofthe lines 400b, 400a, 4001, and the connecting lines 400e and 400d. Theabsence of ground from the sleeve conductors of these lines removes thebusy marking which was previously applied to these lines and batterypotential now extends from the lead H1 through the winding oi! thecutofl relay R4I0 to the sleeve conductors of the above-mentioned lines,whereby these lines are now marked as idle.

When the called party at the substation M restores the telephone, theoperator at the cordless B board 440 is advised by the usual supervisorysignal that the connection may be taken down and, in turn, extends thesupervision over the line 100g to the operator attending the cordcircuit 40. The loop circuit, including the tip and ring conductorsextending to the Jack '450, is thereupon interrupted and that causes thesupervisory relay R430 to restore. In restoring, the relay R490completes, at its contacts 495, a circuit including the contacts 44! forilluminating the supervisory lamp 451. The operator attending the cordcircuit 40 is thus advised to remove the plug 455 from thejack 459, and,when that is done, it removes-the ground potential from the and thecutofl relay R4I0 have been operated. It will also be assumed that theoperator at the cord circuit has received the number of the desired linein the automatic telephone system. To extend this call, the plug 455 isinserted into the jack 459 and ground potential at the lead I" isthereby appliedto the sleeve conductor of the line 59l extending to thetrunk circuit 590, shown diagrammatically in Fig. 5. This groundpotential upon the sleeve conductor marks the Jacks associated with theline 591, including the Jack 959, as busy. This ground potential isapplied through the sleeve relay R440 to the contacts 449 01' the ringkey 442 and the contacts 419 of the switch 410, to the sleeve-ringelement of the plug 455 and to the sleeve of theiack 459. .When thering-sleeve element of the plug 455 engages the sleeve of the Jack 459,the sleeve relay R440 is operated. This circuit may be traced fromground upon the'lead I I! through the sleeve relay R440, the contacts445 and 419, the sleeve of the plug 455 and the sleeve of the jack 459to battery potential, which is not shown, in the trunk circuit 590. Uponoperating, the sleeve relay R440 completes, at its contacts 44!, acircuit including the grounded contacts 499 for illuminating thesupervisory lamp 451.

The trunk circuit 590 and the selector 595 are of conventional type andtunction to extend the call to the line 599 and to maintain a busyground potential on the sleeve of the jack 459. More particularly, theselector 595 responds to impulses which are sent from the dial 449 inthe cord circult 40, this dial 449 being connected by way of thecontacts "I and 412 of the switch 410, to the tip and ring conductorswhich are connected to the plug 455. This connection extends through thejack 459 to the selector-595 by way of the line sleeve of the jack 459and so removes the busy marking from the sleeve conductor of the linei00g. Also, upon removal of the plug 455 from the jack 459, the sleeverelay R440 is restored and opens, atits contacts I, the circuit forilluminating the supervisory lamp 451.

Call from manual, substation MA to automatic substation P In completinga call from the manual substation MA, it will be assumed that the cordcircuit 40 has been used to answer the call on the lines 591, the trunkcircuit 590, and the line 592. The selector 595 responds to the'impulsessent by the dial-445 to position its wipersupon the contacts terminatingthe line 599. More particularly, the impulses produced by the dial 449are conducted -by way oi the contacts "I and 412 of the switch 410, thetip and ring contacts of the plug 455, the jack 459, the lines 591 and592, and the trunk circuit 590, to the selector 595. The selector 595responds to the impulses of the first digit transmitted to elevate thewipers thereof to a position adjacent the row or level of contactsterminating the line 599 which extends to the connector 900. Theselector 595 selects automatically an idle line which extends to one ofthe connectors, and, assuming that the connector 900 is the first idleconnector terminated in the row of contacts selected, the line 599,comprising the conductors 214, 215 and 219, is selected to extend theconnec tion to the connector 900.

The connector 900 is preferably of the wellknown Strowger type, andoperates, in the usual way, to raise the wipers 911", 912 and 919 inresponse to the second digit dialed, to a position adjacent the level inthe connector bank corresponding to the digit dialed. In response to thethird digit dialed upon the calling device 440, the wipers 911, 912 and919 are rotated into engagement with the contacts in the connector bankterminating the line which extends to the called party, and in thepresent example the wipers 911, 912 and 919 are rotated into engagementwith the contacts terminating the conductors 990, "I and 992 of the line900d. If it be assumed that the tor 323, for transmitting busy toneoverthe established connection which extends to the calling substation afterthe operator has restored the switch 410, in a well-known manner. Theoriginal circuit for operating the busy relay R333 passed through thecontacts 352 of the slow-torelease relay R350, which relay restoresafter a short interval to close, at the contacts 353, a holding circuitfor the busy relay R330. This circuit extends from ground upon thecontacts 322, by way of the contacts 332, 353 and 333, through the busyrelay R330 to LV battery upon the conductor !!1. It will be noted thatthe busy relay R333 is connected to the LV battery source whichcorresponds to the battery voltage which is applied to the windings ofthe cutofi relays in the line circuits associated with the linesextending to the connector bank. With the busy relay R330 connected tothe same battery potential as the cutoir relay windings, there is nopossibility of any false operation of the busy relay R330 or the cutoffrelays of idle lines which terminate in the level associated with theline 300d, when the control wiper 313 comes into contact with theterminal connected in circuit with the windings of their cutoff relayswhen the wipers are being rotated to the contacts of a called line.

Upon hearing the busy tone, the subscriber at the manual substation MAreplaces the telephone upon the hook to open the loop circuit extendingto the cord circuit 40. Thereupon, the supervisory relay R425 restoresto complete, at the contacts 426, a circuit including the contacts 42!for illuminating the supervisory lamp 404 which indicates to theoperator at that position that the calling subscriber has disconnectedand that the plug 402 may be withdrawn from the jack 40!. The operatoralso removes the plug 455 from the jack 453, thereby opening the loopcircuit which extends through the trunk circuit 530 and the selector 435to the connector 300, causing the trunk circuit 530, the selector 535and the connector 300 to be restored.

If it be assumed that the called line L303 is idle when called, LVbattery will be connected through the cutofl relay R330 to the controlterminal in the connector bank by way ofthe contacts 331 and throughcontrol conductor 332. The LV battery potential upon the controlterminal of the line 300d short-circuits the'winding of thebusy relaywhich has one terminal connected to the same source of LV batterypotential. After the slow-to-release relay-R350 restores, the switchingrelay R360 is operated over a circuit extending from ground at contarts322 by way of the contacts 33!, the upper winding of relay R360, thecontacts 35!, and

the wiper 313, the control terminal and conductor 332, contacts 331 andthrough the winding of the cutofi relay R330 to LV battery. The cutoffrelay R330 is thus operated to open, at its contacts 33! and'332, .thecircuit of the line relay R335. In operating, the switching relay R330completes, at its contacts 35! and 352, acircuit for conducting ringingpotential to the called line L300 and for preparing the talking circuitto the called substation P. At the contacts 365, the switching relayR330 connects ground potential to the control conductor 332 to mark theline 333d as busy to any other connectors attempting to call this line.The re- -lease relay R3|0 is operated by the line relay,

which is not shown, and completes at the contacts 32! a holdingground'which extends back over the control conductor 213 to maintain theconnector marked as busy to the link 203 and to the selectors in thegroup which'includes the selector 533.

The release and restoration of the manual lease relay R3l0, uponrestoring, removes the holding ground potential at the contacts 32! fromconductor 216, thus causing the selector 535 to restore its wipers tonormal in a well known manner and rendering thetrunk circuit 530available for other calls.

Connection from the automatic substation P to the manual substation MWhen a call is-initiated at the automatic substation P, a loop circuitis completed over the line L303 which causes operation of the line relayR335. This circuit extends from ground by way of the contacts 33!, theconductor 333, the closed loop at the substation P, conductor 33!,contacts 332 and the winding 01' the line relay R335 to HV battery. Theline relay R335 operates to close, at its contacts 333, a circuit forapplying ground potential to the sleeve conductors of the line 300aextending to jacks at the operators positions in the switchboard of Fig.1, including the jack I53, for marking the line 330a and the associatedline L300 as busy to incoming calls from the manual switchboard. Thecontrol conductor 332 is also grounded by the closure or the contacts333, which marks the lines L300 and 303d as, busy inthe banks of theconnectors. The operation of the line relay R335 also closes thecontacts 333 to apply LV battery potential by way of the winding of thecutoil relay R333 to the control conductor of the line 3031 whichextends to the banks of the finder 2!0. Also, the operation of the linerelay R335 closes the contacts 333 to apply ground potential to thestart conductor 30! which extends through its associated resistor 302 tothe distributor 210 to cause the distributor to choose an idle link forthe use of the calling line L330. The ground upon the start conductor30! also marks the level in the vertical bank 253 in which the callingline is located. Assuming that the link 200 is the first idle linkencountered by the distributor 210, the finder 2l0 is first caused tosearch for the level in which the calling line is located. The verticalwiper 255 is raised step by step into engagement successively with thecontacts of the vertical bank 253, until ground potential is encounteredupon one of the contacts of the bank 253. In the present example, groundpotential will be encountered upon the second contact which terminatesthe grounded conductor 33!. The distributor then controls the finder 2!0to search in the selected level for the contacts terminating the callingline, this line being marked with LV battery. When the'wipers of thefinder 2l0 reach the contacts corresponding to the calling line, thecontrol wiperC will encounter LV battery potential upon the contactterminating the C conductor 326 of the line 3001i, which causes thefinder to select the calling line and extend the connection to theselector 220 of the link 200. The finder 2I0, which is preferably of thewell-known Strowger type, in extending the connection to the selector220, causes the switching relay R230 to be operated and close thecontacts 23!, 232, 233 and .234.

The talking connection now extends through the T and R'wipers of thefinder 2 I and through the contacts 23! and 232 of the switching relayR230 to the selector 220. At the contacts 233, ground potential is putupon the control wiper C, to operate the cutofi relay R390 and to markthis line as busy to incoming calls. The relay R24!) is also operated toapp y, at contacts 24!, ground potential to the control conductor 242,thereby holding the switching relay R230 operated by way of the contacts234.

The selector 220, which is also preferably of the well-known Strowgertype, responds to the first digit dialed at the calling station MA, toposition, the wipers 21!, 212 and 213 adjacent the level of contactscorresponding to the number dialed. During the interval between thefirst and second digits dialed, the selector 220 operates automaticallyto select an idle line in the selected group of lines extending to thegroup of connectors in which the connector 300 is included. Assumingthat the connector 300 is selected, the connection is extended theretoby way of the selector wipers 21!, 212 and 213 and the conductors 214,215 and 216 of the line 533 and the connector 300 is prepared for thesecond and the final digits. When the selector 220 is seized, therelease relay R250 is operated to complete, at the contacts 25!, acircuit for extending multiple ground potential over the controlconductor 242 to maintain the switching relay R230 operated, and, atcontacts 252, the control conductors 242 and 213 are connected together.Upon receiving the second digit, the connector 300 responds to selectthe level or group of lines in which the called line is located. Thefinal digit causes the wipers 31!, 312 and 313 to select the contacts inthe connector bank which terminate the desired line, which, in thepresent example, is the line I000! and. the connected line L|00. Thefunctions of the connector 300 with respect to encountering a busycondition upon the line !00d, and with respect to switching through tothe line L! 00 if the line is idle, need not be described as they arethe same as those described in connection with making a call from thesubstation MA and through the cord 40 to the substation P. The train ofswitches including the finder 2! 0, the selector 220, and the connector300, is held operated by the ground which is applied to the controlconductors 216, 325 and 242 at the contacts 32! and 322 upon theoperation of relay R3l0 in the connector 300.

When the connector 300 has selected the line l00d by moving the wipers31!, 312 and 313 into contact with the terminals which terminate theconductors 311, 318 and 319 of the connecting lin l00d, a busy test ismade to determine if the associated line L|00 is in a busy condition. Ifthe line L|00 is busy, ground potential will be found upon the conductor319 of the line l00d. This ground potential will be applied to conductor319 through the winding of the sleeve relay Rl20, the associated plugI02 and the jack !0! if the line L|00 is the calling line; or throughthe winding of the sleeve relay RI50, the associated plug I55 and theJack I56 if the line L|00 is the called line in a manual connection; orby way of the cordless B board if the operator thereat extended a callto the line L|00; or through the associated contacts 365 and the wiper313 of another connector 300 if the line L|00 is called by anotherautomatic subscriber. The busy relay R330 is operated from ground on theconductor 319 over the control wiper 313 and connects, at the contacts324, busy tone to the talk conductor which extends through the selector220and the finder M0 to the calling line L300 and thesubstation P.Assuming, however,

that the connecting line l00d is idle when called, the control wiper 313encounters LV battery upon the control conductor319, which batteryshunts the winding of the busy relay R330 which therefore does notoperate. When the switching relay R360 operates shortly after the busytest to close the contacts 36! and 362 and connect the line conductors311 and 318 to the ringing leads through the contacts 34! and 343, thisswitching relay also applies, at the contacts 365, ground potential tothe control conductor 319. The ground upon the control conductor 319marks the line L|00 as busy to the connectors having access to the line!00d.' Also, the ground upon the conductor 319 is cross-connected at theintermediate distributing frame IDF-Z to the sleeve conductor of theline I00e which conductor terminates upon an A terminal of the maindistributing frame MDF. The sleeve conductors of the lines 00a and l00fare also connected to the sleeve terminals of the main distributingframe MIDF and the ground upon the sleeve of the jack I56 thus marks theline !00a as busy to the operators at the switchboard shown in Fig. l,and the line l00f is marked as busy by the ground placed upon the sleeveconductor which cooperates with the cordless B board 440 to mark thisline busy to the operators at this board. When the switching relay R360operates and connects the line conductors 311 and 8'18 to the ringingleads by way of the contacts 34! and 343, ringing current is transmittedto signal the subscriber at substation M from battery, the interruptedringing generator GEN, the upper winding of the ring cutoff relay R340,the contacts 34! and 36!, the wiper 31!, the tip conductor 31! of theline l00d, the line I 00s, the line L|00, the ringer at the substationM, and returning by way of the ring conductor of the line L|00, the lineI00e,

the line l00d, the ring conductor 318, the wiper 312, and the contacts362 and 363, to ground. When the subscriber at substation M answers thecall, a direct current loop circuit is completed and causes the ringcutoff relay R340 to operate and open its contacts 34! and 343 toterminate the ringing signal. The relay R340 also completes a lockingcircuit for its lower winding (not shown) and, at its contacts 342 and344, it

completes a'talking circuit from the calling sub- Method of converting amanual subscribers line to automatic operation The operations thus fardescribed are those which are based on the assumption that the manualsystems illustrated in Figs. 1 and 4 are still entirely manual inoperation and that they have been connected with the automatic systemshown in Figs. 2, 3 and which may have replaced an old manual system orbe merely an addition to the manual system disclosed, appropriatechanges in polarity in the manual system and changes in voltage in theautomatic system having been made, according to the present invention,to permit the two types of systems to be interconnected and to allow theextension of calls from one portion of the composite system to another.

Consideration will now be given to the operation of the composite systemdisclosed when a manual portion of the system is gradually converted toautomaticoperation. It will be assumed that the manual system shown inFig. 4 is to be thus converted to automatic operation while maintainingits operative connections with the manual system of Fig. 1 and theautomatic system of Figs. 2, 3 and 5.

In converting a manual line such as the line L400 to full automaticoperation, the manual sub station instrument 'at the substation MA isreplaced with an automatic type instrument which includes an impulsetransmitting dial. At the manual switchboard, the answering jack 40l,the line 400b, the manual line circuit 405, and the line 4000 aredisassociated from the line L400, by disconnecting the line 40011 fromthe E terminals of the intermediate distributing frame IDF-l, and bydisconnecting the line 4000 from the D terminals of that intermediatedistributing frame. In the automatic switchboard the line circuit 50! isassociated with the line L000 by connecting the previously installedline 400h which extends from the line circuit 50! to the F terminals ofthe intermediate distributing frame IDF-Z, and by connecting to the Fterminals of the intermediate distributing frame IDF2 the previouslyinstalled line 0007' which then extends from the terminals of the IDF-Zto the bank terminals of the line finder 2 I 0.

The above changes are of minor nature and involve no alterationsor-additions of equipment and are quickly and easily made withoutinterruption of telephone service longer than the time required toreplace the manual telephone instrument with the automatic instrument atthe substation MA and the brief interval required to remove the lines4001: and 0000 and to connect the lines 4001 and 40070.

Completing connection from the converted substation MA to the automaticsubstation P In initiating a call at the converted substation MA, justreferred to, the telephone is removed from the hook switch, whichcompletes a loop circuit extending over the lines L400, 400a and 400k tocause operation of the line relay R520. This circuit may be traced fromground, upon the contacts 5| I, by way of the, tip conductor of the line400h, over the tip conductor of the lines 400e and L400, through thecompleted loop at the substation MA, over the ring conductors of thelines L400, 400e and 400h, through contacts in and the winding of theline relay R520 to H'v" battery. In operating, the line relay R520completes, at its contacts 52L a circuit for applying ground potentialto the sleeve or control MDF.

conductors of the lines 400h, 400e, 400i. and 400a, the sleeve orcontrol conductors of these lines being connected together at thedistributing frames as shown. The ground upon the sleeve of the line400! marks the line L400 as busy to operators in the switchboard of Fig.1 having access thereto by way of the jack H0, and ground upon thesleeve of the line 400a marks the line L400 busy to the operators in theswitchboard shown in Fig. 4, having access thereto by way of the jack456.

When the sleeve or control conductor of the line 400h is grounded, thesleeve conductor of the line 400d is also grounded through thecrossconnections at the intermediate distributing frame IDF-2, extendingbetween the F and G terminals. The grounding of the sleeve or controlconductor 316 of the line 400d marks the connecting line 400:; as busyto the connector switches in the automatic system. The lines 400d and400a are cross-connected between the F and G terminals of theintermediate distributing frame IDF-2-, which connection eifectlvelymarks the line L400 as busy to the connectors as stated above. Upon theoperation of the line relay R520, the contacts 522 are opened, therebyremoving LV battery potential through the relay R5l0 from the sleeveconductors of the lines 400h, 000e, 400a, 400 and 40011; this battery,prior to its removal at the contacts 522, marked the above'lines as idleto their respective points of access, as described. At the same time,the contacts 523 are closed to apply LV battery potential through thecutoff relay R510 to the control conductor 426 of the line 4001, whichextends to the finder bank contacts of the finder 2l0 corresponding tothe calling line L400. It will be noted that the talking conductors ofthe lines 0001' and 000e are connected together at the F terminals ofthe intermediate distributing frame IDF--2 and that the talkingconductors of the lines 800e and L400 are connected together at the Aterminals of the main distributing frame The application of LV batterypotential to the conductor 426 of the line 400 marks the line L400 asthe calling line in the finder banks, whereby the finder is caused toselect the line 4007' which is associated with the line L400.

The contacts 524, upon closing, in response to the operation of the linerelay R520, complete a circuit over the conductor 403 for starting thedistributor 210, which selects an idle link for the use of the callingline. The operation of the distributor 210 and the finder M0 to selectthe calling line 4001 appearing in the finder bank is well known andbriefly described in explaining the extension of a call irom thesubstation P to the converted substation M, so that it need not bedescribed in detail. Also, the progress of the call through the finderM0, the selector 220 and 'the connector 300 to select the connectingline 300d which is associated with the line L300 will not be describedin view of the previous description given of a call through theseswitches.

In making calls through the automatic system and, more specifically,when the wipers of the connectors are rotated over the contacts of alevel in search for the contacts of the called line, the wipers may passover a number of contacts which are associated with idle lines. Thecontrol wiper of the connector, in passing over the control contacts ofidle lines, applies LV battery poassociated with the lines.

tential to these contacts as these contacts are passed over by way of LVbattery which is fed from the conductor II'I through the busy relay R330and by way of the contacts 363 and 352 to the control wiper 313 and tothe control contacts being contacted. As stated above, the controlconductors are connected through the various distributing frames andlines to the cutofi relays With the busy relay R330 connected to LVbattery, it will be seen that there will be no potential diiferencebetween the battery connected to the busy relay R330 and thebattery-connected cutoif relays in the line circuits. Therefore, as theconnector control wiper successively makes contact with the controlcontacts of lines in passing over, the busy relay R330 and the cutoffrelays of the lines will not be falsely operated.

However, if the busy relay R330 were connected to HV battery potentialwhile a cutoff relay, for example, such as the manual cutofi relay RI I0, is connected to LV battery potential, then, upon movement of thecontrol wiper 313 into contact with the bank contact which terminatesthe conductor 319 (assuming these contacts are on the same.level andprecede the contacts 382), there would be a potential diilerence betweenthe LV battery upon the cutoff relay RI l and the HV battery upon thebusy relay R330. This circuit extends from the LV battery potential uponthe relay RIIO, from the conductor I I1, by way of the winding of the'relay RI I0, the sleeve conductors of the lines I000, I00c, I00e andI00d, the conductor 319, wiper 313, contacts 352, 363 and the winding ofthe busy relay R330 to HV battery potential. From the foregoing, it willbe seen that with both the relays R330 and the cutoff relays of the linecircuit connected to the same battery potential, these relays areprevented from false operation when the control wiper 313 encounters thecontrol conductors of line circuits.

The release of the connection between the converted substation MA andthe automatic substation P need not be described in detail since it iseffected in the manner usual to the release of connections of lines inan automatic telephone system. With respect to the release of the switchtrain, however, it is noted that the control conductors 216 and 325 aredisconnected at the contacts 32! and 322 when the release relay R3I0 isrestored and, likewise, that the control conductors 242 and 216 aredisconnected at the contacts 25I and 252 when the release relay R250 isrestored. This arrangement whereby the control conductors 216 and 325are disconnected acts, upon release of the connector 300, to preventground potential from being conducted over these control conductors inseries to the control wiper 313 during its return to normal position.Ground potential upon the conductor 325 during the period of release ofthe connector might cause improper operation of certain apparatus, suchas the. switching relay R360 and the cutoff relays in line circuitswhich may be momentarily connected upon restoration of the connector300.

From the foregoing description of how a manual line is converted to aline of the automatic typ as applied to the line L400, it will be seenthat the line LI 00 may also beconverted to automatic operation byreplacing the substation instrument at the substation M with asubstation of the automatic type, by disconnecting the lines I00c andI00b from the intermediate distributing frame IDF-I and by connectingthelines I001, I007 to the F terminals of the intermediate distributlngframe IDF-2 in a manner similar to that by which the line L400 and itsassociated lines are connected when the line L400 is converted toautomatic operation.

Connection from the automatic substation P to the converted substationMA In completing a connection from the substation P to the substationMA, after theisubstation MA has been converted to automatic operation,the operation of the switching apparatus is similar to that described inconnection with a call from the substation P to the substation M.However, in making a call to the substation MA, the manual line circuit405 (Fig. 4) is disconnected and the line circuit 50I (Fig. 5) isconnected to the lines 40011 and 400e in accordance with the conversionplan described above. When the wipers of the connector 300 come intoengagement with the contacts terminating the conductors 314, 315 and 316of the line 400d, and the switching relay R360 operates, ground isapplied by way of the contacts 365 and the wiper 313 to the sleeveconductor 316 of the connecting line 400d. Ground potential on theconductor 316 is extended through the cross-connections at theintermediate distributing frame IDF-2 to the sleeve conductors andground is thereby extended through the contacts 522 and the winding ofthe cutofi relay R5I0 to LV battery. The cutofi. relay R510 operates tointerrupt, at .its contacts 5H and 5I2, the circuit for energizing theline relay R520. The ground potential on the control conductor 316 ofthe line 400d is extended to the sleeve conductor of the line 400e byway of the intermediate distributing frame IDF.-2 and this sleeveconductor is connected to an A terminal of the main distributing frameMDF which also terminates the sleeve conductors of the lines 400) and400a. Thus, the line L400 is marked busy at the jack I58 and 456 to theoperators at the switchboards shown in Figs. 1 and 4. The method ofreleasing the above connection is the same as that conventionallypracticed in automatic telephone systems, and the apparatus forrestoring the switches used in making the connection has not been shownfor this reason.

Although one embodiment of the improved telephone system and certainexamples of the improved method of conversion from manual to automaticoperation have been shown and described by way of illustration, it willbe understood that the improved system is capable of other embodimentsand that the improved method may be practiced in various ways withoutdeparting from the scope of the appended claims.

I claim:

1. In a communication system, a manual telephone system including manuallines terminating in jacks at operator controlled switchboards, saidjacks each including a sleeve element whereon the busy condition of theassociated line may be marked by the presence of a characteristicpotential, cord circuits at said switchboards having plugs forengagement with said jacks, means in said cord circuits including saidplugs for applying said characteristic potential to a sleeve element ofsaid jacks, an automatic telephone system including line selectingswitches having sets of contacts for terminating lines of both saidautomatic and said manual systems, said sets of contacts each includinga control contact whereon the busy condition of the associated line maybe marked by the presence of a characteristic potential which issubstantially different from the first-mentioned characteristicpotential, means in one of the telephonesystems for altering its busycharacteristic potential to render' it substantially the same as thebusy characteristic potential of the other system, and means a forinterconnecting the two telephone systems.

, tomatic lines and said manual lines, said contact sets each comprisinga pair of line contacts and a control contact, means in each of saidline selecting switches and including said control contacts for markingsaid automatic lines as busy by applying a second characteristicpotential upon said control contacts, said first characteristicpotential being of opposite polarity to said second characteristicpotential, .means in one of,

the systems for changing the polarity of the characteristic potential ofthat system to agree with the polarity of the other system, and meansfor interconnecting the two systems together,

3. In a communication system, a manual telephone exchange having manuallines terminating in jacks, cord circuits at said exchange having plugsfor engagement with said jacks, a group of manual line circuits eachassociated with one of said manual lines, a first power source connectedto said manual exchange, an automatic exchange having line selectingswitches terminating automatic lines, a group of automatic line circuitseach associated with one of said automatic lines, a second power sourceconnected to said automatic exchange, means for interconnecting saidexchanges to permit calls to be completed between said exchanges, saifirst power source being normally connected to said manual exchange withits polarity in opposed relation to that in which said second powersource is connected to said automatic exchange, and means for alteringcertain connections of said first power source to said manual exchangeto cause the polarity of corresponding lines in the two exchanges toagree.

4. In a communication system, a manual telephone exchange having manuallines terminating in jacks, cord circuits at said exchange having plugsfor engagement with said jacks, a group of manual line circuits eachassociated with one of said manual lines, a first power source connectedto said manual exchange, an automatic exchange having line selectingswitches terminating automatic lines, a group of automatic line-circuitseach associated with one ofsaid automatic lines, a

5. In a communication system, a manual telephone exchange including aplurality of manual lines terminating in Jacks, a group of manual linecircuits each associated with one of said manual lines, cord circuits atsaid exchange provided with plugs for engagement with said jacks,control apparatus in said cord circuits including relays for controllingsupervisory devices, a first power source at said exchange connected tosaid line circuits and to said control apparatus including said relays,an automatic exchange comprising automatic lines and switches forcompleting connections to said automatic lines, a group of automaticline circuits each associated with one of said automatic lines, a secondpower source connected to said switches and to said automatic linecircuits, the polarity of said second power source being normallyconnected in opposite relation to that in which said first power sourceis connected, means for interconnecting the two exchanges comprisingconnecting lines corresponding to said manual lines and said automaticlines of the two systems to permit the lines in each exchange to callthe lines in the other exchange, said connecting lines being associatedwith said jacks and with said automatic switches and comprising two lineconductors and a control conductor, and means in said manual exchangefor altering the polarity of the connections of said first power sourceto said relays and to certain parts of said manual line circuits,thereby causing corresponding connected lines in the two exchanges tohave the same polarity.

6. In a communication system, a manual telephone exchange, a pluralityof manual lines terminating in jacks, cord circuits at said exchangeprovided with plugs for engagement with said jacks, said jacks eachcomprising two line elements and one control element, line and controlapparatus in said cord circuits, a manual line circuit associated witheach manual line, a first power source connected to said controlapparatus in each of said cord circuits and each of said manual linecircuits, an automatic telephone exchange comprising a plurality ofautomatic lines and automatic line selecting switches terminating saidautomatic lines, said automatic switches each including a set of lineterminating contacts each associated with one of said automatic lines,each set of said contacts comprising two line contacts and one controlcontact for each automatic line, a second source of power different inpotential and opposite in polarity from said first power source andconnected to apparatus in said line selecting switches, an automaticline circuit associated with each of said automatic lines, means forinterconsecond power source connected to said automatic necting said twoexchanges comprising connecting lines corresponding tothe manual linesand to the automatic lines in the two systems through which the lines ineach exchange have access to the lines in the other exchange, saidconnecting lines each including two line conductors and a controlconductor which are adapted 'to be connected with said jack elements insaid manual exchange and said line terminating contacts in the automaticexchange, means in said manual exchange for reversing the polarity ofsaid first power source connected to points in said line and controlapparatus in said cord circuits and to said manual-line circuits, andmeans in said line selecting switches in the automatic exchange foraltering the potential applied to apparatus therein and to saidautomatic line circuit.

7. In a communication system, a manual teleeach terminating upon a setof manual line terminating contacts and a jack, cord circuits at saidmanual exchange each provided with plugs for engagement with said jacks,each plug including two line elements and one control element, line andcontrol apparatus in each cord circuit, a manual line circuit associatedwith each manual line, a power source connected to said line and controlapparatus in said cord circuit and to each of said manual line circuits,an automatic exchange having a plurality of automatic lines, a

plurality of automatic line selecting switches having contacts uponwhich said automatic lines terminate, an automatic line circuitassociated with each of said automatic lines, a second source of powerconnected to said automatic switches and to said automatic linecircuits, said second source of power being different in potential andopposite in polarity from said first source of power, a plurality offirst connecting lines each associated with contacts in said automaticswitches and with a corresponding one of said manual line terminatingcontacts, an automatic jack inthe manual exchange for each automaticline, a plurality of second connecting lines each associated with one ofsaid automatic jacks and with one of said automatic lines, means in saidmanual exchange for reversely connecting the polarity of said firstpower source to said line and control apparatus in said cord circuitsand to each of said manual line circuits to agree with the polarity ofthe connections of said second power source, and means in said lineselecting switches for altering the potential of said second powersource connected to apparatus in said switches and to said.

automatic line circuits to agree with the potential of said first powersource.

8. In a communication system, a manual exchange including a plurality oflines terminating in three-element jacks, a two-conductor cord circuitcomprising two element plugs together with supervisory equipment andcontrol equipment, said plugs being adapted to eengage with said jacksto answer and extend calls, aimanual line circuit for each of saidlines, a first power source connected to said supervisory equipment andcontrol equipment and to said manual line circuits. an automaticexchange including a plurality of automatic lines terminating in contactsets of automatic switches, an automatic line circuit for each of saidautomatic lines, a second power ,power source connected to power sourceconnected to'said supervisory and control equipment and to said manualline circuits, an automatic exchange comprising automatic switcheshaving contact sets at which a plurality of automatic lines terminate,an automatic line circuit for each of said automatic lines, a secondpower source connected to said automatic switches and to said automaticline circuits, an automatic three-element jack at said manual exchangefor each of said automatic lines, means including three-conductorconnecting lines for connecting together said line terminating contactsof said manual lines with corresponding contacts of said automaticswitches, other connecting lines for connecting said contacts of saidautomatic switches with corresponding elements of said automatic jacksin said manual exchange, said first power source being normallyconnected to said equipment in the manual exchange with its.polarity inopposition to that of said second said automatic switches and saidautomatic line circuits, and means in said manual exchange for reversingsaid first power source connections to said equipment in said manualexchange to agree with the polarity of said power source connected tosaid automatic switches and said automatic line circuits.

10. In a telephone system comprising a manual exchange, an automaticexchange, and connecting lines for interconnecting apparatus in themanual exchange with related apparatus in the automatic exchange, saidmanual exchange comprising a plurality of manual lines, a manual linecircuit for each manual line, an operator switchboard, and a first.power source in said manual exchange for operating said manual linecircuits and apparatus in said operator switchboard, said automaticexchange comprising a plurality of automatic lines, an automatic linecircuit for each automatic line, and an automatic switchboard, saidautomatic switchboard including apparatus operable in connection withrelated apparatus in said manual exchange over said connecting lines,and a second power source for operating apparatus in said automaticswitchboard-which is of substantially the same voltage as that of saidfirst power source.

11. In a telephone system'comprising a manual exchange, an automaticexchange, and connect source connected to said automatic switches and Ito said automatic line circuits, and means including three-conductorconnecting lines for connecting together said two exchanges byconnecting .said manual lines with contacts of said automatic switchesand by connecting saidautomatic lines to corresponding elements of saidjacks in said manual exchange, said first power source being connectedto said manual line circuits and to said supervisory and controlequipment in said manualexchange with its polarity in agreement with thepolarity of said second power source connected to said automaticswitches and said automatic line circuits.

9. In a communication system, a ma nual exchange including a pluralityof manual lines terminating in line terminating contacts and inthree-element Jacks, a three-conductor cord circuit comprisingthree-element plugs connected with supervisory equipment and controlequinment, said plugs being adapted to engage with said jacks to answerand extend calls, a. manual line circuit for each or said manual lines,a. first ing lines for interconnecting apparatus in the manual exchangewith related apparatus in the automatic exchange, said manual exchangecom-' prising a plurality of manual lines, a manual line circuit foreach manual line. an operator switchboard, and a first power source insaid manual exchange for operating said manual line circuits andapparatus in said operator switchboard, said automatic exchangecomprising a plurality of automatic lines. an automatic line circuit foreach automatic line, and an automatic switchboard, said automaticswitchboard including cooperating apparatus operable in connection withrelated apparatus in said manual exchange over said connecting lines,and a second power source for operating apparatus in said automaticswitchboard which is of substantially the same voltage as said firstpower source, additional apparatus in said automatic exchange, a secondpower sourceof substantially the same voltage as that of said firstpower source for operating said cooperating apparatus insaid automaticexchange, and an additional power source for operating said additionalapparatus.

HARRY P; MAHONEY.

